geant4 tools and interfaces from elshield project

Geant4 tools and interfaces

from ELSHIELD project S. Ibarmia(1), V. Ivantchenko(2), A. Howard(2), D. Heynderickx(3)

(1) National Aerospace Technology Institute, INTA (2) Geant4 Associates International, G4AI

(3) DH Consultancy

9th Geant4 Space User’s Workshop

Barcelona, 4-6 March 2013

9th Geant4 Space Users’ Workshop Barcelona, 4-6 March 2013

ELSHIELD

Geant4 Tools

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ELSHIELD Project Energetic Electron Shielding, Charging and Radiation Effects and Margins

An ESA funded activity (Galileo program) with the aim to improve the performance of

deep/internal dielectric charging tools, review EM physics simulation for energetic

electrons and develop interfaces and utilities to couple plasma and HEP tools.

Review of EM physics in Geant4, focusing on energetic electrons (MeV).

Comparing models with existing electron data, other MC codes & tools.

Proposing improvements to current EM models and new I/F options

Analysis of electron dose enhancement effects in multi-layer structures

New experimental datasets obtained and preliminary G4 simulations

New EM and geometry biasing options

Coupling Geant4/GRAS with ESA space charging tool (SPIS)

Internal dielectric (SPIS) + charge transport (G4)

New interfaces

SPENVIS, FASTRAD, Geant4/GRAS, SPIS

New generation look-up table tools for rapid effects calculations

Automated tool to optimize payload arrangement

Introduction. ELSHIELD outcomes


ELSHIELD

Geant4 Tools

Review of EM physics.

Model improvements & new I/Fs


ELSHIELD

Geant4 Tools Review of EM physics. New models & I/Fs

• Analysis the existing Geant4 EM models

Simple 1-D, 3-D cases were built for benchmarking

The theoretical basis of the models was identified

Comparisons with EGS and Penelope2008 data

Geant4 results were validated vs. evaluated data and dedicated

experimental benchmarks

Weak or missing models were identified

A set of improvements was proposed:

MSC and the single scattering models. Extension of exiting models

A new bremsstrahlung model

New interfaces to the atomic de-excitation models

Atomic de-excitation combined with photo-electric and Compton effects

PAI and Moller-Bhabha extended below 1 keV

• In addition, an e- irradiation campaign was performed to obtain dose profiles

in multi-layer shieldings and compare to results from new EM Geant4 models


ELSHIELD

Geant4 Tools

Standard EM model improvements:

New bremsstrahlung model for G4SeltzerBergerModel

New version of L.Urban multiple scattering G4UrbanMscModel95

New model of photo-electric effect G4PEEffectFluoModel (Atomic de-excitation added)

New model of Compton scattering G4KleinNishinaModel (Atomic de-excitation and Doppler added)

New angular generator G4DipBustGenerator (Fast sampling of angular distribution for bremsstrahlung)

Extension of PAI and Moller-Bhabha ionisation models down in energy from 1 keV to 100 eV (Important

for micrometer scale simulation)

New EM interfaces:

Universal interface to angular generator (Interchange of angular generators between models)

New universal interface to atomic de-excitation (Standard EM package can use de-excitation module)

New EM biasing framework (Biasing options are available via UI commands)

All these available since Geant4 v.9.5

More details about models validation and UI commands in Vladimir’s talk

(Wednesday)

Review of EM physics. New models & I/Fs


ELSHIELD

Geant4 Tools

Conclusions

As a result of ELSHIELD project Geant4 EM physics become

uniform, more stable and more precise

The default physics list (Opt0) is High Energy Physics oriented

Standard Physics List Opt3 can be used for accurate study of

shielding effects

Livermore and Penelope Physics Lists are equivalent in CPU

speed and physics capabilities to the Standard Opt3

Review of EM physics. New models & I/Fs


ELSHIELD

Geant4 Tools

Experimental electron dose

enhancement

Comparison with G4 EM models


ELSHIELD

Geant4 Tools

Date

New experimental data was obtained during ELSHIELD

(TRAD was in charge of experimental campaigns)

Typical electron energies in GEO/MEO scenarios

0.1 to 10 MeV range

Common shielding materials in the space domain

Al, Ti, Cu, Ta

Multilayer shielding combining high-Z / low-Z

Ta-Al, Cu-Al, Ti-Al

Analyzing deposited dose under different shielding depths

Comparing Data vs Geant4 and Penelope 2011

Experimental dose enhancement effects


ELSHIELD

Geant4 Tools

Date

Ref Name

Total

Thickness

(mm)

Description

1 32 Al 8 32 aluminium layers

2 20 Ti 5 20 titanium layers

3 8 Cu 2 8 copper layers

4 4 Ta 1 4 tantalum layers

5 Ta – 16 Al 4.25 Single tantalum layer followed by 16 aluminium layers

6 Ta - 4 Al (2x) 2.5 Single tantalum layer followed by 4 aluminium layers (2x)

7 Ti – 4 Al (4x) 5 Single titanium layer followed by 4 aluminium layers (4x)

8 Cu – 24 Al 6.25 Single copper layer followed by 24 aluminium layers

Experimental Test Samples



ELSHIELD

Geant4 Tools

Date

Experimental Irradiation Setup

Electron Energy 1 MeV 3 MeV 6 MeV 10 meV

Facility /

Accelerator TU Delft

Van de Graaff Elekta Synergy Linac

Distance beam

source to samples 15 cm 100 cm

Beam irradiation

area 300 x 500 mm2 250 x 250 mm2

Beam spectral

shape Mono-Energetic

FWHM < ±3% Standard Elekta Synergy Beam

Beam spatial

profile Gaussian

± 5% Standard Elekta Synergy Beam

Top plate Aluminium 20 mm

Plastic Water WTe

12 mm

Plastic Water WTe 23

mm

Base plate Aluminium 2 cm Plastic Water WTe 10 cm

Atmosphere Air

Expected total

dose 100 kGy 2 kGy

Measured total

dose at control

dosimeter 135.1 119.4 1.48 1.56



ELSHIELD

Geant4 Tools Experimental dose enhancement effects


ELSHIELD

Geant4 Tools

Atomic de-excitation has no significant impact on dose profiles, but slight differences in the tail

Opt0 and Opt3 provide similar results when production cut is set to 1.0 micron

As expected , G4Penelope seems to provide a better agreement with Penelope-2011

Similar results are obtained for other EM models (Opt4, Penelope, Livermore)


Geant4 modelling. Geant4 vs Penelope-2011


ELSHIELD

Geant4 Tools

Date

TU-Delft Setup

– Base plate 20 mm Al

– Window 100 micron Al

– World filled of dry air

– Control Dosimeter (blue) next to

4th column (4Ta)

– Samples placed according Test

Setup

– Primary electrons

• 1.035 MeV (sigma 0.01)

• 3.03 MeV (sigma 0.01)

– Simulated events: ~1E5/cm2

Geant4 modelling



ELSHIELD

Geant4 Tools

Geant4 modelling. Data vs G4Penelope



ELSHIELD

Geant4 Tools

Geant4 and Penelope-2011 vs Data



ELSHIELD

Geant4 Tools

Date

Good agreement between both codes

Electron and photon spectra are similar but for very low energies

Different mechanisms and values to simulate low energy particles producation:

geometrical cuts (G4) and absorption energies (Penelope)


Where do the differences G4 – Penelope2011 come from?


ELSHIELD

Geant4 Tools

Date

Good agreement between both codes

As in the 2 mm depth case, electron and photon spectra are still similar but for very low

energies



ELSHIELD

Geant4 Tools

Date

Significant differences in the electron spectra (Geant4 spectra attenuated ~20-30%)

Electron spectra dominated by primaries

MSC modelling diferences becomes significant

Photon spectra are still similar

Photon production almost similar for both codes



ELSHIELD

Geant4 Tools

Date

Again, predicted electron spectra by both codes agree

No primary electron is present.

Spectra is dominated by secondary electrons

Predicted photon spectra are still similar

Photon production is almost equivalent in both codes



ELSHIELD

Geant4 Tools

Date

Conclusions

Total dose for high energy electrons is dominated by

primary particles in the e- range region, low shielded layers, and then it

depends strongly on electron propagation modelling

Bremmstrahlung photons for high shielded layers showed low dependence on

EM model.

Major differences between EM Models comes from MSC modelling

Atomic de-excitation has no significant impact on total dose predictions

Optimum production cut, for total dose calculations, is found to be

1 micron for Opt0 and Opt4

1 to 100 micron for Opt3, Penelope and Livermore

Best EM candidates for space radition shielding

Opt3 and Penelope

Futher analysis of Geant4 MSC models should be done



ELSHIELD

Geant4 Tools

Geant4 I/Fs to SPIS

Arbitrary geometry scoring


ELSHIELD

Geant4 Tools Geant4 I/F to SPIS

To develop a SPIS to Geant4 interface that:

Extends G4/GRAS to read SPIS mesh geometries

Converting SPIS meshes to Geant4 geometry

Fully command-line driven

and allowing G4 simulation on SPIS mesh ed volumes

(using parallel scoring worlds)

To develop a SPIS to Geant4 interface that:

Extends G4/GRAS to read SPIS mesh geometries

Converting SPIS meshes to Geant4 geometry

Fully command-line driven

and allowing G4 simulation on SPIS mesh ed volumes

(using parallel scoring worlds)

Return Geant4 results to SPIS:

Providing radiation effects in terms of

Deposited dose (fconductivity)

Charge (transport, poisson eqs)

For each mesh cell of SPIS geometry

Output results in a SPIS compliant format

Return Geant4 results to SPIS:

Providing radiation effects in terms of

Deposited dose (fconductivity)

Charge (transport, poisson eqs)

For each mesh cell of SPIS geometry

Output results in a SPIS compliant format


ELSHIELD

Geant4 Tools

SPIS Mesh Reader & G4ScoringUserGeom

New set of “Persistency” C++ classes → GmshGeometry family

GmshGeometryReader, GmshElement, GmshNode, etc

To read and parse GMSH “.msh” ASCII files.

Compatible with GMSH 2.x series.

Based on Gmsh 2.5 specification. Tested with Gmsh 2.5 for Linux

All GMSH sections are parsed and stored in a GmshGeometry object

Mandatory: $MeshFormat, $Nodes, $Elements

Optional: $ElementData, $NodeData

Additional $Data sections can be added

New GRAS geometry constructor → GRASGmshGeometry

New G4 scoring mesh geometry → G4ScoringUserGeom

SPIS Mesh Reader & G4ScoringUserGeom

New set of “Persistency” C++ classes → GmshGeometry family

GmshGeometryReader, GmshElement, GmshNode, etc

To read and parse GMSH “.msh” ASCII files.

Compatible with GMSH 2.x series.

Based on Gmsh 2.5 specification. Tested with Gmsh 2.5 for Linux

All GMSH sections are parsed and stored in a GmshGeometry object

Mandatory: $MeshFormat, $Nodes, $Elements

Optional: $ElementData, $NodeData

Additional $Data sections can be added

New GRAS geometry constructor → GRASGmshGeometry

New G4 scoring mesh geometry → G4ScoringUserGeom

Geant4 I/F to SPIS


ELSHIELD

Geant4 Tools

/gras/geometry/type gdml

/gdml/file/ test_geom.gdml

/gras/analysis/mesh/addModule MyMesh

/gras/analysis/mesh/MyMesh/geometryType gmsh

/gras/analysis/mesh/MyMesh/geometryFile test.msh

/gras/physics/setCuts 0.01 mm

/gras/physics/addPhysics em_lowenergy

/gps/position 25 0 0 mm

/gps/direction -1 0 0

/gps/particle e-

/gps/energy 20.00 MeV

/run/beamOn 10000

/score/open MyMesh

/score/quantity/cellCharge charge C

/score/quantity/doseDeposit doseDep Gy

/score/quantity/energyDeposit eDep MeV

/score/verbose 0

/score/close

Results

Dose, Charge and Energy deposited per mesh cell

Gmsh formatted

Visualized with GMSH Linux tool

Geant4 I/F to SPIS


ELSHIELD

Geant4 Tools

Deposited Energy Visulaization with GMSH post-processing tool

Geant4 I/F to SPIS


ELSHIELD

Geant4 Tools

GRAS-SPIS Charging Interface

New GMSH “.msh” file reader classes available for Geant4 and GRAS

New generic G4ScoringUserGeomFile to score quantities in arbitrary

geometry volumes user-defined (GDML, GMSH, C++)

Other scoring geometry formats can be easily added is parsing classes

are developed

New GRASMeshAnalysisModule

Loads GMSH, GDML files as parallel scorers

Outputs analysis results in a SPIS-GMSH compliant format

GRAS-SPIS Charging Interface

New GMSH “.msh” file reader classes available for Geant4 and GRAS

New generic G4ScoringUserGeomFile to score quantities in arbitrary

geometry volumes user-defined (GDML, GMSH, C++)

Other scoring geometry formats can be easily added is parsing classes

are developed

New GRASMeshAnalysisModule

Loads GMSH, GDML files as parallel scorers

Outputs analysis results in a SPIS-GMSH compliant format

Geant4 I/F to SPIS


ELSHIELD

Geant4 Tools

New tools:

Automated payload

arrangement inside a S/C


ELSHIELD

Geant4 Tools

Objectives

Analysis of the impact of different payload arrangement solutions in the total

deposited dose in selected locations

Using an automated optimization algorithm

Genetic Algorithms + Geant4 Reverse Monte Carlo

Study case

Representative 5 boxed-payload inside a simple generic S/C

Usingas input typical MEO electron environment

And optimizing TID at a selected component inside one of the boxes

Automated Payload Arrangement


ELSHIELD

Geant4 Tools

G4-GA algorithm basics

GA chromosomes store information for XYZ coordinates of a box

GA gens specifies the position of all boxes in 3D

Typical GA-G4 sequence:

An initial population is generated: discrete XYZ sets

Selection of a generation

A GDML geometry is generated using XYZ defined by genes/chromosomes

Impossible geometries are discarded (G4 Overlapping,etc)

Reverse MC is started

Fitness function: minimum dose (f = 1 – TID/TIDmax-allowed)

Apply GA common techniques to produce a new generation

Crossover, mutation, elitism



ELSHIELD

Geant4 Tools

Simple S/C

+

5 Electronic Boxes



ELSHIELD

Geant4 Tools

Main parameters Name of the initial GDML file

List of boxes (volume names) to be

included in the analysis

Name of target volume

(X,Y,Z) ranges for moving boxes

Maximum allowed dose for normalising

fitness function

Name of the macro file with the

environment spectrum

GA specific parameters

Geant4 specific parameters

Date

&GAEES

binpath='./runGRAS.sh'

maxgen=20

microga=1

npopsiz=50

DoseMax=1.0E13

nXDivs=64

nYDivs=64

nZDivs=64

nBoxes=5

XMIN=-120.0

XMAX=120.0

YMIN=-120.0

YMAX=120.0

ZMIN=-120.0

ZMAX=120.0

outDir='.'

outname='SIMPLE_01'

gdml='Simple_SC.gdml'

targetVolume='Box4_PCB1_DetectorSi_PV'

adjointSurface='Box4_PCB1_DetectorSi_PV'

extSurfRadius=499

extSurfRadiusUnit='mm'

primarySpectrum='primarySource.g4mac'

dosePrecision=5

saveNumEvents=10000

adjointNumEvents=1000000

grasEnvScript='./env_elshield.sh'

grasBinary='./grasGA'

grasMacDir='./macros'

grasGeomDir='./geometry'

/



ELSHIELD

Geant4 Tools

• ##################### Generation 1 #######################

• # Box X Y Z Value

• 1 1 22.5000 151.8750 -151.8750 0.749

• 1 2 -168.7500 -78.7500 -126.5625 0.880

• 1 3 -104.0625 -16.8750 109.6875 0.170

• 1 4 -59.0625 112.5000 -28.1250 0.851

• 1 5 -30.9375 56.2500 16.8750 0.379

• Fitness: 0.8541

• Total Dose: 1.459E+11 MeV

• ===============================================================

• 2 1 16.8750 -154.6875 168.7500 0.721

• 2 2 160.3125 -126.5625 -137.8125 0.373

• 2 3 -73.1250 -16.8750 -112.5000 0.658

• 2 4 -104.0625 53.4375 78.7500 0.094

• 2 5 101.2500 -129.3750 135.0000 0.298

• Fitness: 0.0000

• Total Dose: -1.000E+33 MeV

• ===============================================================

Date



ELSHIELD

Geant4 Tools

Date

• ######################################################

###

• Summary of Output

• Generation Evaluations Avg. Fitness Best

Fitness

• 1 5 0.3616 0.9540

• 2 10 0.8766 0.9548

• 3 15 0.8779 0.9596

• 4 20 0.8778 0.9548

• 5 25 0.5617 0.9981

• 6 30 0.5685 0.9980

• 7 35 0.9683 0.9997

• 8 40 0.5973 0.9997

• 9 45 0.3680 0.9997

• 10 50 0.5382 0.9998

Final output results

4.7 E10 MeV

2.05 E8 MeV



ELSHIELD

Geant4 Tools

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A review of electron EM physics models in Geant4 has been performed,

providing new refinements and new interfaces to manage them

New datasets for electron dose enhancement effects in multi-layer

structures are available

Comparisons to Geant4 EM models aleady done.

New geometry interfaces allow G4/GRAS to read complex Gmsh meshes

and perform radiation calculations on them

Parallel scoring is now possible for arbitrary geometries: Gmsh, GDML and

C++ user-defined

Preliminary assessment of 3D GA-based techniques seem to be a very

promising approach to get automated shielding optimization tools.

SUMMARY & CONCLUSIONS

geant4 tools and interfaces from elshield project

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